Nearly 500 people, mostly children, have tested positive for HIV in southern Pakistan, Al Jazeera reports. A local doctor, who also tested HIV positive, has been arrested and is being investigated for intentionally infecting his patients, though he denies the charges.

In Pakistan, HIV is most commonly spread as a result of reused syringes and unsanitary medical conditions. The growing popularity of quack doctors compounds the problem, according to UNAIDS, which notes that nearly 600,000 are operating in the country.

“Rampant medical malpractices without any effective checks and balances are causing repeated outbreaks in Pakistan,” Bushra Jamil, an infectious disease expert at the Aga Khan University in Karachi, told Al Jazeera.

Until recent years, Pakistan saw low levels of HIV prevalence. But that is changing quickly. About 20,000 new HIV cases were reported in 2017 alone. In fact, Pakistan now has the second fastest-growing HIV rate in Asia.

Further complicating the situation, Pakistan is experiencing a surge in population, and many people do not have access to quality health care, especially those who live in impoverished rural communities and are more vulnerable to quack doctors.